The UK's most complete GLP-1 guide
Every Question Answered. Every Side Effect Explained.
- How GLP-1 medications work
- Mounjaro vs Wegovy compared
- Injection instructions
- Side effects & solutions
- What to eat on treatment
- FAQs answered
Free tracker included with every download this week
Liquid Diet and Weight Loss — What You Need to Know
A liquid diet involves consuming only liquids—such as water, juice, broth, or meal replacement shakes—instead of solid food. While some people use liquid diets for gradual weight management, the NHS emphasises that sustainable weight management in the UK typically requires balanced nutrition alongside lifestyle changes. Liquid diets can support short-term weight loss but are most effective when combined with professional guidance and a plan to transition back to normal eating. Our free BMI calculator can help you track your current health baseline and weight loss goals as you explore different approaches.
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Calculate Your BMI Instantly
Enter your height and weight below. Supports both imperial (stone & lbs) and metric (kg). Results include NHS category, healthy weight range, and ethnicity adjustments.
What Is BMI and Why Does It Matter?
Body Mass Index (BMI) is the most widely used screening tool for assessing whether your weight falls within a healthy range. Used by the NHS, GPs, and weight management services across the UK, BMI provides a quick snapshot of your weight relative to your height. The formula is simple: your weight in kilograms divided by your height in metres squared (kg/m²).
While BMI isn't a perfect measure — it doesn't account for muscle mass, bone density, or fat distribution — it remains the standard first step in identifying potential weight-related health risks including type 2 diabetes, cardiovascular disease, high blood pressure, and certain cancers.
The NHS also recommends adjusted thresholds for people of South Asian, Chinese, or Black African heritage — a BMI of 23 or above is classified as overweight, and 27.5 as obese. Our calculator includes this adjustment as a one-click toggle.
How Liquid Diets Work for Weight Loss
Liquid diets create a calorie deficit by replacing solid meals with lower-calorie liquids, leading to rapid initial weight loss. The NHS recommends losing weight at a rate of 0.5 to 1 kg per week for sustainable results, though liquid diets may produce faster short-term loss.
- Very low calorie liquid diets (VLCD): Under 800 kcal per day—only suitable under medical supervision, typically for specific clinical situations
- Meal replacement shakes: Structured programmes using branded shake products, often 500–1200 kcal daily
- Juice cleanses and broth-based diets: Lower kcal but may lack essential nutrients
Weight loss from liquid diets is often rapid initially due to loss of water and glycogen, not just fat loss. For sustainable weight management in the UK, the NHS recommends pairing any dietary change with increased physical activity and behaviour change support.
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care — from a UK-regulated online pharmacy.
How It Works
Three simple steps to understand your weight and take action.
Enter your height and weight in our free calculator. Get your BMI, NHS category, healthy weight range, and ethnicity-adjusted thresholds instantly.
If your BMI suggests you're overweight or obese, explore our GLP-1 calculators to project potential weight loss on Mounjaro or Wegovy.
Use our progress tracker to log your weight weekly, visualise your journey with charts, and stay motivated — all stored privately in your browser.
Free Weight Loss Tools & Guides
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
Liquid Diet Safety and NHS Guidance
Liquid-only diets can cause nutritional deficiencies, muscle loss, and fatigue if followed for extended periods without medical oversight. The NHS advises consulting your GP before starting any restrictive diet, especially if you have diabetes, heart conditions, or take regular medications.
Very low calorie liquid diets may be prescribed by NHS specialist services for short periods (typically 12 weeks) in specific clinical situations, but are not recommended as a long-term weight loss strategy. For sustainable weight management in the UK, most people benefit from balanced nutrition, regular physical activity, and behaviour change support. If you're exploring weight loss options, your GP can discuss whether prescription weight loss medication, structured dietary programmes, or specialist services might be appropriate for your individual health needs.
- Dual GIP/GLP-1 receptor agonist
- Up to 22.5% body weight loss (SURMOUNT-1)
- Weekly injection, dose escalation over 20+ weeks
- Available via private prescription in the UK
- Doses: 2.5mg → 5mg → 7.5mg → 10mg → 12.5mg → 15mg
- GLP-1 receptor agonist
- Up to 15–17% body weight loss (STEP trials)
- Weekly injection, 5-step dose escalation
- NHS & private prescription available
- Doses: 0.25mg → 0.5mg → 1mg → 1.7mg → 2.4mg
Mounjaro vs Wegovy: Head-to-Head
A side-by-side comparison of the two most popular GLP-1 weight loss medications available in the UK.
| Feature | Mounjaro | Wegovy |
|---|---|---|
| Drug class | Dual GIP/GLP-1 agonist | GLP-1 agonist |
| Active ingredient | Tirzepatide | Semaglutide |
| Avg. weight loss | 15–22.5% | 12–17% |
| Key trial | SURMOUNT-1 (2022) | STEP 1 (2021) |
| Max dose | 15 mg weekly | 2.4 mg weekly |
| Escalation period | 20–32 weeks | 16–20 weeks |
| Administration | Weekly injection (pen) | Weekly injection (pen) |
| NHS availability | Private prescription only | NHS & private |
| Approx. private cost | £150–£250/month | £150–£300/month |
| Common side effects | Nausea, diarrhoea, constipation | Nausea, vomiting, diarrhoea |
Data sourced from SURMOUNT-1 and STEP 1 clinical trials. Costs are approximate and vary by provider. Always consult a prescriber.
Am I Eligible for Weight Loss Medication?
In the UK, eligibility for GLP-1 weight loss medications like Mounjaro and Wegovy is based on your BMI and overall health profile.
- BMI of 30 or above (obese)
- Age 18 or over
- No contraindicated conditions
- Committed to lifestyle changes
- BMI of 27 or above
- Plus type 2 diabetes
- Or high blood pressure
- Or obstructive sleep apnoea
Use our BMI calculator to check whether your BMI falls within the eligible range.
How We Built These Tools
Every calculator and guide on myweightcheck is built with accuracy and transparency in mind. Our BMI calculator uses the standard WHO formula with NHS-aligned category thresholds. Our GLP-1 projections are modelled on published clinical trial data from SURMOUNT and STEP studies.
All data stays on your device. We don't require sign-ups, and we don't store your health information on any server. Your progress tracker saves data locally in your browser using localStorage, so only you can see it.
We're based in the UK and our tools are designed specifically for UK users — supporting stone & lbs by default, referencing NHS guidelines, using NICE-approved medication data, and linking to GPhC-registered pharmacies.
Frequently Asked Questions
Common questions about BMI, weight loss medications, and our free UK tools.
Can you lose weight on a liquid diet?
Yes—liquid diets typically create a significant calorie deficit, resulting in rapid initial weight loss. However, much of the early loss is water and glycogen, not fat. For sustainable weight management, the NHS recommends slower, steady loss of 0.5–1 kg per week combined with lifestyle changes and professional support.
Is a liquid diet safe long-term?
No. Extended liquid-only diets can cause nutritional deficiencies, muscle loss, and metabolic slowdown. The NHS advises that any restrictive diet should be discussed with your GP first, especially if you have existing health conditions or take medications. Very low calorie liquid diets are only recommended under medical supervision for short periods.
What's the difference between a liquid diet and meal replacement shakes?
A liquid diet may include water, juice, broth, or any liquid. Meal replacement shakes are structured programmes using specific branded products designed to provide balanced nutrition at controlled calories (typically 500–1200 kcal daily). Structured programmes are generally safer than unsupervised liquid-only approaches.
How does a liquid diet compare to weight loss injections like Wegovy?
A liquid diet is a short-term dietary approach; Wegovy is a prescription-only GLP-1 injection for weight management. Wegovy clinical trials showed average weight loss of approximately 15% body weight over 68 weeks, alongside diet and activity changes. Both require commitment to lifestyle change—your GP can advise which approach suits your individual health needs.
Should I try a liquid diet before seeing my GP?
No. Always consult your GP before starting any restrictive diet, particularly if you have diabetes, heart disease, or take regular medications. Your GP can assess your health, discuss safe options including prescription weight loss medication or NHS weight management services, and provide professional guidance on sustainable weight management in the UK.
Ready to take control of your weight loss journey?
Start with a free BMI check, explore your GLP-1 options, or begin tracking your progress today. No sign-up. No cost. Just results.